Manufacture of cyanids.



L1. METZGER.

MANUFACTURE 0F CYANIDS.

APPLICATION FILED MAR- 7. 1919. 1,322, 195, Patented Nov. 18,1919.

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FLOYD J. METZGEB, OF NEW YORK, N. Y., ASSIGNOR T0 AIR REDUCTION COMPANY, INC., A CORPORATION OF NEW YORK.

MANUFACTURE 0F CYANIDS.

Specification of Letters Patent.

Patented Nov. 18, 1919.

w Application filed March 7, 1919. Serial No. 281,119.

To (1U whom, it may concern:

Beit known that I. FLOYD J. METZGER, a citizen of the United States, residing at New York, in the county of Ne'w York, State of New York, have invented certain new and usefulImprovements in the lllanufacture of .vaniils; and I d o hereby declare the following to be a full, clear, and exact description of the invention. such as will enable others skilled in the artto which it appertains to make and Iuse the same.

`his invention relates to a method of improving the production of cyanids such asA sodium cyanid by directly combining an alkali metal compound with carbonaceous material in the presence of nitrogen or nitrogenous gases.

It has been proposed to manufacture alkali metal cyanids from mixtures of alkali metal coni'pounds, arbonaceous materials and nitrogen by vthe aid of relatively large amounts of catalytic agents such as metallic iron. The iron is mixed with the furnace charge and varies in amount from 33 to 40% by weight of the total charge, the remainder of which is made up of alkali metal compound and carbonaceous material which form the basis of the cyanid. In the de scriptions of such prior proposals the iron has been referred to as a solvent for the carbon and owing to the limited solubility of carbon -in iron,. a large amount of iron has been considered necessary.

T he' employment of so large an amount of iron is objectionable 'for various reasons. Iron does not enter into the composition of alkali metal cyanids and the presence of a large amount thereof limits the effective cyanid producing constituents in a furnace charge of given weight, so that only a lim ited yield of cyanid is obtainable. A large amount of iron moreover is present in the furnace product and the extraction of the cyanid is complicated by the formation of ferro-cyanid,y if the furnace product is leached with water. The resulting contamination of the cyanid extracted renders the product practically worthless for many purposes. The etl'ect thereforeof the use of relatively large amounts of iron is such as to pra"tically preclude the successful opera tion of the process on a commercial sca e.

The present invention has for its object the provision of a method of obtaining cyanid, which overcomes the disadvantages of prior proposalsfatid results in an increased yield of substantially pure cyanid so that thc method becomes commercially practicable.

Further objectsand advantages of the invention will be apparent as it is better uur derstood by reference. to the following specitication. when read in connection with the accompanying drawing illustrating an apparatus adapted to be employed in practising the method. In the drawing:

Figure 1 is a longitudinal section through the apparatus;

F ig. 2 is asection on the line 2-2 of Fig. l; and A Fig. 3 is a section on the line 3-3 of Fig. 2.

According to the present invention the cyanid producing operation is carried out in the presence of a relatively small amount of iron. for example and preferably about 2% by weight of the total furnace charge. remainder of the charge is made up of carbonaceous material such as coke" and an alkali metal compound such as soda ash in the proportions of about 54 parts of coke andI 44 parts of soda ash by weight. Substantially the entire charge. therefore. is made up of active agents effective in the cyanid producing operation and appearing in the product. As a result increased yields of cyanid are obtainable and the cyanid can be. extracted from the furnace product in a state of comparatively high purity and without any material loss of cyanid, as ferrocyanid` or contamination of the cyanid by ferro-cyanid.

The amount of iron employed as a catalyst may be varied somewhat and may. for example, be less than 2% if it is properly and intimately distributed throughout thel furnace charge. Quantities of iron as high as of the tot-al furnace charge, or even more` may be used but I have obtained the best results with an amount corresponding to about 2% of the furnace charge. The iron should lic en'iployed in such a. form that it can be uniformly and intimately distributed throughout the furnace charge. Metallic iron in powdered form is not wel adapted for such intimate distributiona'nd I do not recommend that it be used. I have obtained good results with .reducible iron compounds such as -iron oxid or iron ore and by the use of iron precipitated from solutions in the form' of redncible precipitates. Iron ore or oxid is to be recommended .tively fine condition in any suitable appal ratus adapted to the purpose. Preferably the material is ground so that substantially all of the material passes a 100 mesh sieve, and finer grinding is beneficial to the process and assists in the accomplishment of the desired objects.

'Following the grinding of the material, the various ingredients are mixed in a dough mixer or other suitable mixing machine. Preferably the solid ingredients are first roughly mixed in a dry state and after a suitable amount of water has been placed in the mixer, the dry materials are added thereto while the mixer is in operation until the mass has a creamy consistency. Sutlicient dry mixture is then gradually added and the mixing operation continued until the mass contains only sufficient moisture to hold the particles together in a more or less granular or nodular condition. After drying,`the furnace charge is then ready for treatment to accomplish the desired reaction.

Alternatively the iron may be added in the form of a soluble iron salt. either directly to the water in the mixer, or pref'A erably as a previously prepared solution. For example. ferrous sulfate (green vitriol) may be dissolved in water and supplied in quantity sufficient to provide substantially 2% of iron calculated on the weight of the furnace charge. to the earbonaceous material. and until the latter is thoroughly saturated therewith. A slight excess of alkali hydroxid or carbonate in solution is then added to precipitate the iron as hydroxid or carbonate within the pores of the carbonaceous material. The mixture is then washed to remove sulfatos or other soluble. constituents. rPhe material after drying is mixed with the alkali metal compound in a dough mixer as previously described until the mass assumes a granular or nodular condition.

The` reaction is preferably carried out in a specially designed furnace illustrated in the drawing in which 1 indicates a suitable combustion chamber of fire brick or other usual material adapted to withstand the high temperatures. The combustion chamber is preferably lined with a highly refractory material 2. One or more cylindrical retorts 3 are arranged to extend through the combustion chamber. the retorts being provided with flanges 4 and 5 resting on suitable roller bearings (i and 7.. The retorts are inclined as indicated` in the draw ing and roller bearings 8 are provided to maintam them in proper relatlon to the combustion chamber. Preferably the retorts,

or at least such portion thereof as are sub-` vand on shafts 1() which may be actuated from any suitable source of power. Preferably, to limit the cost of the retorts 3. the portions 11 thereof extending beyond the combustion chamber may be constructed of iron or other suitable metal, welded. or otherwise fastened two the resistant alloy sections.

rPhe retorts 3 are closed at. their lower ends by heads 12 which may be fastened by bolts 13. preferably ot' a character which permits easy removalof the heads to discharge the contents of the retorts. Inlets 1l for the nitrogenous gas are supported in stuffing boxes 15 secured to the heads 12 and flexible tubes 1li are connected to the inlets 1-1 and to a suitable source of the nitrogenous gas under the desired pressure. The tubes 16 are preferably supported on the 4combustion chamber 1 by bracketsl 17, and are of such a character as to maintain the inlets 1J( stationary duringl the rotation of the retorts Il.

Heat is supplied in the combustion chamber. preferably, by the combustion of gas from any suitable source such as the gas producer 18. The gas is conveyed through a suitable conduit 19 and admitted through inlets 2() t0 the combustion chamber; The combustion supporting air is supplied through passages 21 and inlets 22, the air being mixed with the producer gas, which is burned in the combustion chamber. The hot combustion products after circulation about the retorts 3 escape to passages 23 and are conveyed through passages 24 to a regenerator. wherein the waste heat is employed in heating the combustion support ing air prior to its delivery to the combustion chamber. Preferably, the regenerator comprises a plurality of partitions 25, 26 and 27 having air passages 28 therein. The combustion products circula-te about the partitions 25, 26 and 27 and are finally discharged through an outlet 29 to the chimney (not shown). The passage of the combustion gases through the regenerator may be controlled through a suitable dalnper 30 adapted to be manually actuated to accomplish the desired result. The air is admitted at 31 and conveyed through the air passages 28 and finally discharged through a passage 32 communicating with the air passages 21.

The furnace, as thus constituted, provides for the direct utilization of a relatively inexpensive fuel 1n a preheated condition while the combustion supporting air 1s readily pre-heated by the waste combustion gases. It, therefore, becomes possible to maintain the relatively high temperature required in the. combustion chamber without increasing the expense of operation beyond a commercially practicable point.- All parts of the furnace are relatively simple in design and well adapted for the purposes for which they are intended. .The only expensive feature is the retort of resistant metal which is necessarily employed to withstand the corrosive action of the furnace charge heated therein. l

In carrying out the cyanid producing operation, the furnace charge proper as hereinbefore described is disposed in the retort or retorts 3, substantially filling the saine as indicated in Fig. 1 of the drawing. The retorts are rotated preferably at about 1 R. I. M. and are subjected to a combustion temperature of from 1050o to 11000 C. The actual temperature of the material within t-he retorts is maintained in the neighborhood of 950O to 1050o C. Throughout the operation nitrogen or nitrogenous gas under a pressure of about 1 of mercury is admit-ted to the retorts through the inlets 1-L and permeates the mass of material therein, reacting therewith to produce cyanid. The carbon monoxid, uncombined nitrogen and anyother gases formed during the reaction are permitted'to escape through Vthe open charging ends of the `retorts. The rate at which the nitrogen is fed, may, in an apparatus adapted to discharge from 300 to 400 pounds of the mixture at the completion of each operation, yvary between 2 and 3 cu. ft. per minute. The retorts in such an apparatus would be `substantially 15 ft. in length over all, about 7 ft. heilig exposed within the combustion chamber.

During the operation, the furnace charge shrinks from 25 to 30% and in the normal operation the product will consist of from to 30% of sodium cyanid, 8 to 12'/ of sodium oxid and 12 to 15% of sodium carbonate, the remainder being carbon. From -lO to 50% of the total furnace charge is soluble,` the remainder being coke, ash and iron. The furnace product is discharged in a granular or nodular condition which permits leaching thereof in any suitable manner. Leaching may be carried out with water or other solvent, such, for example as the composite solvent, described in my application for Letters Patent No. 182,642 filed July 25, 1917 and consisting of water and an organic solvent, miscible therewith, such as, alcohol, acetone and the like. Owing to the employment of limitedA uantities of iron in the furnace char e, I (find that, although the reaction is acce erated and the yield of cyanid increased, no appreciable amount of ferro-cyanid contaminates the finished product.

From the foregoing description of the invention it will be noted that the employment of a small amount of iron as a catalyst is advantageous,not only in the cyanid producing operation itself, but also in the subsequent extraction ofthe furnace product or in the treatment of` such furnace product for the production of ammonia and foi-mates. Due to the small amount of iron present, the objections incident to the formation of any considerable amount of ferro-cyanid are avoided and increased vields of products of high purity are obtainable.

Thile other metals than iron can be employed as catalysts in the production of cyanids, I consider iron in the form hereinbefore described most advantageous bccause of its availability in the form desired and in sufficient quantity at low cost for 'the connnercial production of cyanids.

This application is a continuation in part of my earlier application, Serial Number 182611, `filed July 25, 1917, and allowed December 23, 1018, which earlier application it is my intention to labandon in favor -of the present application.

My invention as described in saidearlier i application relates broadly to the production of alkali metal cyanid from mixtures of carbonaceous material, alkali metal compound and relatively small proportions o iron when heated in the presence of nitrogen, and various changes may be made in the method as hereinbefore described and in the apparatus employed without departing from theA invention or sacrificing any of its material advantages.

I cla'imz- P 1. The method of manufacturing alkali metal cyanids which comprises heating a mixture of carbonaceous material, alkali metal compound and finely divided iron in the presence of nitrogen gas to a temperature appropriate to the formation of alkali metal cyanid, the amount of finely divided iron being so small that no appreciable amount of ferro-cyanid is formed when the furnace product is leached with an aqueous solvent.

2. The method of n'ianufacturing alkali met-al cyanids which comprises heating a mixture of carbonaceous material and alkali metal compound together with about two to five per cent. of finely divided iron in the presence of nitrogen gas to a temperature appropriate to the formation of alkali metal cyanld.

3. The method of manufacturing alkali metal cyanids which comprises lheatin a mixture of carbonaceous material, alali metal compound and. about two per cont.

of finely divided iron in the presence of nitrogen gas to a temperature appropriate to the formation of cyanid.

4. The method of manufacturing sodium cyanid which comprises heating a mixture of carbonaceous material and sodium carbonate together With about two per cent. of finely divided iron in the presence of nitrogen gasA to a ten'iperature appropriate to the production of sodium cyanid.

5. The method of manufacturing alkali metal cyanids which comprises heating a mixture of carbonaceous material, alkali metal compound and finely divided iron in the presence of nitrogen gas to a temperalture appropriate to the Jformation of alkali metal c vanid, the amount of finelydivided iron being so small that no appreciable mount of ferro-cyanid is formed when the furnace product is leached With an aqueous solvent, extracting the resulting product with a suitable solvent and thereby obtaining a solution of cyanid free from any appreciable' amount of ferro-cyanid.

6. The method of manufacturing alkali metal cyanide which comprises heating a mixture of carbonaceous material and alkali metal compound together with about two to five per cent, of finely divided iron in the presence of nitrogen gas to a temperature appropriate to the formation of alkali metal cyanid, extracting the resulting product with a suitable solvent and thereby obtaining a solution of cyanid free from any appreciable amount of ferro-cyanid.

7. The method of manufacturing alkali metal cyanids which comprises heating a mixture of carbonaceous material, alkali metal compound and about two per cent. of finely divided iron in the presence of nitrogen gas to a temperature appropriate to the formation of cyanid, extracting the resulting product with a suitable solvent and thereby obtaining a solution of cyanid free from any appreciable amount of ferrooyanid.

8. The method of manufacturing sodium cyanid which comprises heating a mixture of carbonaceous materia] and sodium carbonate together with about two per cent. of nely divided iron in the presence of nitrogen gas to a temperature appropriate to the.produc tion of sodium cyanid, extracting the resulting product with a suitable solvent and thereby obtaining a solution of cyanid free from any appreciable amount of ferrocyanid.

9. The method of manufacturing alkali metal cyanids which comprises, mixing a furnace charge containing carbonaceous material, an alkali metal compound and an iron catalyzer, with sufficient liquid to promote the coinmingling of the ingredients, drying the furnace charge, and heating said charge in the presence of nitrogen and at a temperature appropriate to the formation of cyanid, the quantity of iron catalyzer being relatively limited so that no appreciable amount of ferro-cyanid is formed When said charge is leached with an aqueous solvent.

10. The method of manufacturing alkali metal cyanids which comprises mixing a furnace charge, containing carbonaceous material, an alkali metal compound and an iron catalyzer, with sufficient liquid to promote the con'nningling of the ingredients, drying the furnace charge and heatin said charge in the presence of nitrogen an at a temperature appropriate to the formation of cyanid, the quantity of said catalyzer being limited to provide from two to five per cent. of metallic iron in said charge.

11. The method of manufacturing alkali metal cyanids which comprises mixing a furnace charge containingl carbonaceous material, an alkali metal compound and an iron catalyzer, with sufficient liquid to promote the comniingling of the ingredients, drying the furnace charge, heating said charge in the presence of nitrogen and at a temperature appropriate to the formation of cyanid, the quantity of said catalyzer being limited to provide substantially two per cent. of metallic iron in said charge, and extracting the furnace product with a solvent, thereby obtaining a solution of cyanid free from any appreciable amount of ferro-cyanid.

12. The method of nianufacturing alkali metal cyanide which comprises heating a 1mixture consisting of substantially fifty-four parts of carbonaceous material, forty-four parts by Weight of an alkali metal compound and two parts of an iron catalyst, 1n the presence of nitrogen and at a temperature appropriate to the formation of cyanid.

13. The method of manufacturing alkali metal cyanids which comprises preparing a furnace charge consisting of a carbonaceous material, an alkali metal compound and not more than five per cent. of an iron catalyzer, intimately commingling the constitutents of the charge in the presence of Water and subsequently heating the charge in the presence of nitrogen to a temperature appropriate to the formation of c vanid.

14. The method of manufacturing alkali metal cyanids which comprises, preparing a furnace charge consisting of a carbonaceous material, an alkali metal compound and a relatively small proportion of an iron catalyzer, intimately connningling the constitutents of the charge in the presence of Water and subsequently heating the charge in the presence of nitrogen to a temperature appropriate to the formation of cyanid.

In testimony Wlierof I affix my signature.

AFLOYD J. METZGER; 

